use std::time::{Duration, Instant};
fn main() {
    let mut count = 0;
    let time_limit = Duration::new(1, 0); //时间间隔一秒
    let start = Instant::now(); //系统时钟

    while Instant::now() - start < time_limit {
        count += 1;
    }
    println!("{}", count);
}
